Piezoelectric device



Feb. 11, 1941. E. GERLACH I 2,231,159

PIEZOELEC'TRIC DEVICE Filed Nov. 2'7, 1937 INVENTOR [kW/N Gil/16H BY W ATTORNEY Patented Feb. 11, 1941 UNITED STATES.

2,231,159 rmzomnc'mlc nsvlca Application November 21. 1m, Serial No. 176,781

In Germany December 12, 1938 1 Claim. (Cl. 111-321) This invention relates to a new sound device, more especially to a microphone. A

As is known, certain crystals reveal a piezoelectriceflect, i. e. electric tensions are produced a when they are subjected to a compression or tension and, vice versa, deformations of the crystal occur when applying thereto electric tensions.

Now, it was found that also rubber placed between two electrodes produces considerable electric ten- 10 sions, if mechanical oscillations such as, for instance, acoustic oscillations act upon the rubber piece such that the oscillations produce tension stresses or compression stresses in the rubber piece. The electric tensions evidently are caused I l by effects that are similar to the piezoelectric actions of the crystals so that presumably a certain orientation of the rubber molecules takes place durins the manufacturing process of the rubber, for instance. at the rolling of the. plate 20 from natural rubber.

In accordance with a further feature of the invention, the piezoelectric action is increased by causing the rubber solution to freeze in an electricalneld. Itisalsopossibletovulcaniaetherubesberinanelectricalfleld. 'Inerubbermassis caused to harden between plates to which evenage is applied.

The accompanylni flaure illustrates a microphone as example embodyins the idea of the in vention. The microphone body I exposed to I acoustic oscillations consists of rubber, the voltare produced being derived by means of the electrodes 2. In order to assure apossibly favorable picking up of this voltage, a thin metal layer 3 is preferably applied to the rubber piece and a thin metal foil is to be placed between the electrodes and the rubber piece.

What is claimed is:

The method of producinz an element which 15 when subjected to mechanical stresses will provide electrical tensions and vice versa which includes the steps of, freezing a rubber solution to obtain solid rubber, and subiectin: said solution to an electrical ileld durina said freeains process to to so orient therubbermolecules astoenhancethe ability of said element to provide electrical tension when subjected to mechanical stresses and vice versa. I

g ER.WIN GERLACH. 

